In traditional rotary machine applications, wireless monitoring systems are necessary in order to validate system level models, provide condition based monitoring and may be used for asset control. In order to increase the fidelity and/or reliability of the sensed data that is obtained by a sensor, multi-channel sensing systems are preferred. Surface acoustic wave (SAW) sensing systems are ideal for rotary applications as SAW systems among other things, SAW systems can be interrogated via wireless means, are inherently passive, and do not require the use of batteries or other energy harvesting techniques at the sensing point of the system. These attributes make them sensor candidates in areas where movement and/or hot environments preclude the use of wired and/or conventional electronics. A key attribute associated with passive sensing systems such as SAW sensing systems is that of efficient radio frequency (RF) coupling. Improved communication of sensed data between the sensor system and a reader disposed away from the sensor system can be achieved through an optimal RF coupler antenna design within the sensing system.
One issue with multi-channel sensing systems is cross-talk between two or more channels. Cross-talk between channels of the sensing system causes issues because each one channel can cause interference to an adjacent channel. This interference can reduce the measurement accuracy of the sensing parameter or if the interference is severe enough, may render the system unusable. Another issue with wireless multi-channel sensing systems is establishing and maintaining electrical coupling between a rotor antenna and a stator antenna, and between a rotor antenna and a reader that is disposed away from the sensing antenna. A rotor antenna that does not maintain signal connectivity with a reader through the stator antenna will provide inaccurate, sporadic, or not data whatsoever.